Combine tab background image getter code into one place.

chrome/browser/ui/views/tabs/tab_controller.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_UI_VIEWS_TABS_TAB_CONTROLLER_H_
 #define CHROME_BROWSER_UI_VIEWS_TABS_TAB_CONTROLLER_H_
 
 #include "chrome/browser/ui/views/tabs/tab_strip_types.h"
 
 class Tab;
@@ skipping 78 matching lines @@
                                  const ui::MouseEvent& event) = 0;
 
   // Returns true if |tab| needs to be painted. If false is returned the tab is
   // not painted. If true is returned the tab should be painted and |clip| is
   // set to the clip (if |clip| is empty means no clip).
   virtual bool ShouldPaintTab(const Tab* tab, gfx::Rect* clip) = 0;
 
   // Returns true if tabs painted in the rectangular light-bar style.
   virtual bool IsImmersiveStyle() const = 0;
 
+  // Returns the resource ID for the image to use as the tab background.
+  // |custom_image| is an outparam set to true if either the tab or the frame
+  // background images have been customized; see implementation comments.
+  virtual int GetBackgroundResourceId(bool* custom_image) const = 0;
+
   // Adds private information to the tab's accessibility state.
   virtual void UpdateTabAccessibilityState(const Tab* tab,
                                         ui::AXViewState* state) = 0;
 
  protected:
   virtual ~TabController() {}
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_TABS_TAB_CONTROLLER_H_